Hot graphite dust in the inner regime of NGC 4151

ABSTRACT We model the near-infrared (NIR) spectral energy distribution (SED) of NGC 4151 with a 3D radiative transfer skirt code, using which torus only (TO) and ring and torus (RAT) scenarios are studied. In the RAT models, a graphite ring-like structure (clumpy or smooth) is incorporated between the torus and the accretion disc. We vary the inclination angle (i), inner radius (of the torus and the ring, Rin,t and Rin,r, respectively), torus half-opening angle (σ), optical depth ($\tau _{9.7, \rm t}$ of the torus and $\tau _{9.7, \rm r}$ of the ring), and the dust clump size (Rclump). We perform a statistical analysis of the parameter space and find that all the models are able to explain the flat NIR SED of NGC 4151 with minor differences in the derived parameters. For the TO model, we get Rin,t = 0.1 pc, σ = 30°, i = 53°, $\tau _{9.7, \rm t} = 10$, and the clumpsize, Rclump = 0.4 pc. For the smooth RAT model, $R_{\rm in, \rm r} = 0.04$ pc and $\tau _{9.7, \rm total}$ = 11 and for the clumpy RAT model, Rin,r = 0.04 pc/0.06 pc and $\tau _{9.7, \rm total} = 20$. The Rin,t from the TO model does not agree with the NIR observations (∼0.04 pc). Hence, the most likely scenario is that a hot graphite ring is located at a distance 0.04 pc from the centre, composed of a smooth/clumpy distribution of dust followed by a dusty torus at 0.1 pc with interstellar medium type of grains.

Sabella spallanzanii and Seafloor Biodiversity Enhancement in a Marine Soft-Sediment System

Predicting and managing the potential economic, social, and ecological impacts of bioinvasions is a key goal of non-indigenous species (NIS) research worldwide. The marine fan worm, Sabella spallanzanii, is an ecosystem engineering NIS that forms dense filter-feeding canopies on hard substrata and large clumps of individuals in soft sediment habitats. In this study, we investigated the epifaunal assemblages associated with Sabella clumps of increasing size and complexity from soft-sediment benthic ecosystems in Auckland Harbour, New Zealand. The diversity and abundance of epifaunal taxa increased with clump size. Species accumulation curves suggest that with further increases in Sabella clump size, diversity will continue to increase. There were no differential effects on taxa related to feeding mode or motility despite the potential for Sabella to reduce food to suspension feeders (through competition) and increase food supply to deposit feeders (through biodeposition). Our results provide an example of local biodiversity enhancement by an NIS, though some of the species benefitting from Sabella were themselves non-indigenous or of uncertain origin (cryptogenic/indeterminate). Longer term studies of the impacts of Sabella on native biodiversity and ecosystem functioning, including on food webs, are important next steps.

Radiative equilibrium estimates of dust temperature and mass in high-redshift galaxies

ABSTRACT The estimation of the temperature and mass of dust in high-redshift galaxies is essential for discussions of the origin of dust in the early Universe. However, this is made difficult by limited sampling of the infrared spectral-energy distribution. Here, we present an algorithm for deriving the temperature and mass of dust in a galaxy, assuming dust to be in radiative equilibrium. We formulate the algorithm for three geometries: a thin spherical shell, a homogeneous sphere and a clumpy sphere. We also discuss the effects of the mass absorption coefficients of dust at ultraviolet and infrared wavelengths, κUV and κIR, respectively. As an example, we apply the algorithm to a normal, dusty star-forming galaxy at z = 7.5, A1689zD1, for which three data points in the dust continuum are available. Using κUV = 5.0 × 104 and $\kappa _{\rm IR}=30(\lambda /100\,\mu{\rm m})^{-\beta }$ cm2 g−1 with β = 2.0, we obtain dust temperatures of 38–70 K and masses of 106.5–7.3 M⊙ for the three geometries considered. We obtain similar temperatures and masses from just a single data point in the dust continuum, suggesting that the algorithm is useful for high-redshift galaxies with limited infrared observations. In the case of the clumpy sphere, the temperature becomes equal to that of the usual modified black-body fit, because an additional parameter describing the clumpiness works as an adjuster. The best-fitting clumpiness parameter is ξcl = 0.1, corresponding to ∼10 per cent of the volume filling factor of the clumps in this high-redshift galaxy if the clump size is ∼10 pc, similar to that of giant molecular clouds in the local Universe.

The Evaluation of M/M/2 Queuing Framework with Two Heterogeneous Servers for Balking and Reneged Customers

Queuing hypothesis is a quantitative method which comprises in building scientific models of different sorts of lining frameworks. Occupied time of the framework is broke down and mean holding up time in the stationary system processed. At long last, some numerical outcomes are introduced to demonstrate the impact of model parameters on the framework execution measures. The traveling server, nonetheless, comes back to landing which is used to offer at a low rate whereas the other server is occupied. At whatever point the framework ends up and the subsequent server leaves for a working excursion while the principal server stays inert in the framework. These models can be utilized for making expectations about how the framework can change with requests. The framework is examined in the enduring state utilizing lattice geometric strategy. The clients enter the line in the Poisson manner and the time of each bunch size is dared to be circulated exponentially as for mean ward clump size and clients may balk away or renege when the holding up the line of the clients, in general, be exceptionally enormous. This work exhibits the investigation of a recharging input different working excursions line with balking, reneging and heterogeneous servers. Queuing hypothesis manages the investigation of lines and lining conduct. Different execution proportions of the model, for example, anticipated framework length, anticipated balking rate and reneging rate have been talked about. The technique breaks down an M/M/2 lining framework with two heterogeneous servers, one of which is constantly accessible however the different travels without clients sitting tight for service. During a working vacation period, the subsequent server gives administration at a slower rate as opposed to totally ceasing service. The relentless state probabilities of the model are advantageous and recursive strategies.

The chaotic wind of WR 40 as probed by BRITE

ABSTRACT Among Wolf–Rayet stars, those of subtype WN8 are the intrinsically most variable. We have explored the long-term photometric variability of the brightest known WN8 star, WR 40, through four contiguous months of time-resolved, single-passband optical photometry with the BRIght Target Explorer nanosatellite mission. The Fourier transform of the observed light curve reveals that the strong light variability exhibited by WR 40 is dominated by many randomly triggered, transient, low-frequency signals. We establish a model in which the whole wind consists of stochastic clumps following an outflow visibility promptly rising to peak brightness upon clump emergence from the optically thick pseudo-photosphere in the wind, followed by a gradual decay according to the right-half of a Gaussian. Free electrons in each clump scatter continuum light from the star. We explore a scenario where the clump size follows a power-law distribution, and another one with an ensemble of clumps of constant size. Both scenarios yield simulated light curves morphologically resembling the observed light curve remarkably well, indicating that one cannot uniquely constrain the details of clump size distribution with only a photometric light curve. Nevertheless, independent evidence favours a negative-index power law, as seen in many other astrophysical turbulent media.

2D wind clumping in hot, massive stars from hydrodynamical line-driven instability simulations using a pseudo-planar approach

Context. Clumping in the radiation-driven winds of hot, massive stars arises naturally due to the strong, intrinsic instability of line-driving (the line-deshadowing instability, hereafter LDI). But LDI wind models have so far mostly been limited to 1D, mainly because of the severe computational challenges regarding calculation of the multi-dimensional radiation force. Aim. In this paper we simulate and examine the dynamics and multi-dimensional nature of wind structure resulting from the LDI. Methods. We introduce a pseudo-planar, box-in-a-wind method that allows us to efficiently compute the line force in the radial and lateral directions, and then use this approach to carry out 2D radiation-hydrodynamical simulations of the time-dependent wind. Results. Our 2D simulations show that the LDI first manifests itself by mimicking the typical shell structure seen in 1D models, but that these shells quickly break up into complex 2D density and velocity structures, characterized by small-scale density “clumps” embedded in larger regions of fast and rarefied gas. Key results of the simulations are that density variations in the well-developed wind are statistically quite isotropic and that characteristic length scales are small; a typical clump size is ℓcl∕R*~ 0.01 at 2R*, thus also resulting in rather low typical clump masses mcl ~ 1017 g. Overall, our results agree well with the theoretical expectation that the characteristic scale for LDI generated wind-structure is on the order of the Sobolev length ℓSob. We further confirm some earlier results that lateral “filling in” of radially compressed gas leads to somewhat lower clumping factors in 2D simulations than in comparable 1D models. We conclude by discussing an extension of our method toward rotating LDI wind models that exhibit an intriguing combination of large- and small-scale structures extending down to the wind base.

Clump structure, population structure and non-destructive biomass estimation of the New Zealand carrageenophyte Sarcothalia lanceata (Gigartinaceae, Rhodophyta)

Abstractis a New Zealand carrageenophyte with tetrasporophytic thalli that produce carrageenan very close to the idealised structure of lambda-carrageenan. As such there is interest in its potential for commercial utilisation. There is no information on the biology and ecology of natural populations of this species, but this knowledge is critical for determining whether a species is a suitable candidate for sustainable wild harvest or for aquaculture. Population studies were conducted at two sites in New Zealand’s South Island in order to provide fundamental information on this species. The structure (abundance and composition of male, female, tetrasporophytic and non-reproductive clumps) of the two populations was assessed monthly over a year, and population biomass estimated using regression methods. Seasonal variation was not evident in most of the parameters measured, but differences between sites were found in total population density, the density of different life-history phases, and clump size and structure. The turnover in biomass occurs more frequently at the blade level than at the clump level and the presence of a basal crust in this species promotes population stability.

Biometric and phytochemical variability of roseroot (Rhodiola rosea L.) from field cultivation

Summary Roseroot (Rhodiola rosea L.) is an adaptogenic plant, widely used in the traditional medicine of Scandinavia, Russia, China and Mongolia. The aim of the study was to determine the biometric and phytochemical co-variability of this species under field cultivation in western Poland (Plewiska near Poznań). The plant material originated from four-year-old cultivation established twice by rhizome division in autumn 2007 and 2008. In the study, 46 individuals (23 plants in 2011 and in 2012) were used. The biometric analysis included measurements of the basic characteristics of plants related to the size (luxuriance) of clumps, shoots, leaves and rhizomes with roots (raw material). The amounts of total polyphenols (expressed as gallic acid), tannins (expressed as pyrogallol) and flavonoids (expressed as quercetin) were determined spectrophotometrically. The obtained results showed high variation of Rh. rosea, especially in the level of flavonoids (0.01-0.20% DM) and in the weight of raw material (113-1156 g FM/plant). There were observed correlations between the phytochemical (flavonoid and total phenolic content) and biometric (water content, leaf number, shoot and clump size) features.

Differences in Seed Set and Fill of Cultivars of Miscanthus Grown in USDA Cold Hardiness Zone 5 and Their Potential for Invasiveness

Miscanthus sinensis Andersson has become a very popular ornamental grass used in a variety of horticultural settings, yet in many states it now appears on invasive species lists. Many cultivars have been released with a range of different characteristics that likely increase or decrease their invasive potential in different climates. To determine the fecundity, and by extension, the invasive potential of cultivars currently sold in USDA cold hardiness Zone 5, thirty-one cultivars of M. sinensis (Maiden grass, Chinese silver grass) along with one Miscanthus subspecies cultivar (M. sinensis Andersson subsp. condensatus (Hack.) T. Koyamama ‘Cabaret’), one Miscanthus hybrid (M. × giganteus J.M. Greef & Deuter ex Hodk. Renvoize), and one related species (M. sacchariflorus (Maxim.) Hack.) were transplanted into a common garden at the Chicago Botanic Garden in Cook County, IL, and evaluated for flowering, growth habit, and seed viability. Over the course of the 5-year trial period, 68.1% of all plants survived. Growth in clump size varied greatly among taxa, as did flowering periods. Most cultivars set filled seed, ranging from 14 to 349,327 seeds per plant; only four produced no seed over the course of the trial. Most cultivars of the species represent a high risk for self-seeding in Zone 5. Because Miscanthus sinensis is self-incompatible (8), risk of self-seeding increases when two or more cultivars are grown together. Implications for potential invasiveness are discussed.